I. Field of the Invention
This invention relates in general to antioxidants, and antioxidant synergists for organic materials and in particular to a process for making a phenolic phosphite by reacting a phosphorus trihalide, e.g., PCl.sub.3 and 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene as well as the adducts made thereby.
II. Description of the Prior Art
Phosphites are used in organic polymers and other organic substrates as high temperature antioxidants. The phosphites are generally considered better than phenolic antioxidants at high temperatures because they eliminate hydroperoxides which decompose and lead to autooxidation chain reactions. Thus phosphites are important for hydrolytic stability during polyolefin extrusion and during other operations with organic substrates.
Various phophites are well known in the art such as the aryl phosphite shown in U.S. Pat. No. 4,282,141 to Minagawa et al, and the phenyl phosphonites disclosed in U.S. Pat. No. 4,233,207 to Spivack.
Phenolic and phosphite antioxidants are often used together in polyolefin homopolymers and copolymers to provide antioxidant protection for both low and high temperature exposure. Unfortunately additional expense is encountered as more additives in larger amounts are needed for a polymer. Thus there exists a need for effective antioxidants at a reasonable additive price, not only for polyolefins but other substrates as well.
Other phosphite antioxidants are those disclosed in U.S. Pat. No. 4,187,212 to Zinke et al, and U.S. Pat. No. 3,039,993 to Friedman.
Various alkylated phenolics are well known in the art such as those disclosed in U.S. Pat. No. 3,026,264. The high temperatures referred to above with regard to phosphites, are high enough to affect the rigidity of a polyolefin, but are generally below the point where the polyolefin would immediately decompose or ignite.